The present invention relates in general to a medical catheter with multiple stiffness sections, and, more specifically, to a medical catheter and an efficient manufacturing method employing bump tubing and a relatively stiffened distal end incorporating radiopaque markers.
Many medical procedures require entry into a patient's blood vessel for purposes of accessing a desired site, e.g., angioplasty, stenting, and other treatments for chronic total occlusions. In order to gain access to the desired site, a catheter is advanced through the blood vessel. Once in place within the patient's vessel, various types of medical instrumentation can be fed through the catheter and positioned at the desired site so that the procedure may be performed.
To initially gain access to a particular site within a patient, a needle is used to puncture the patient's skin and gain entry to a desired blood vessel. During insertion of the catheter through the blood vessels, it may be required to follow a tortuous path. Therefore, the distal end of the catheter has been made more flexible than the proximal end. The flexible distal end provides trackability, while the stiffer proximal end provides pushability. As shown in U.S. Pat. No. 7,896,861, a catheter may include a proximal shaft section of a polymer with a relatively high durometer and a distal shaft section of a polymer with a relatively low durometer. However, mechanical bonding or welding of the different sections creates a potential site for kinking of the catheter.
Bump tubing has been used in catheters to provide a decreased tube diameter at the distal end for navigating small vessels and to provide an increased tube diameter at the proximal end for accommodating medical devices to be used during a medical procedure. Bump tubing, also known as a taper tube, may be formed by extruding a polymeric tube in a manner that varies the diameter during the extrusion. As a consequence of the changing diameter, the tube stiffness is reduced along with the diameter without creating a potential site for kinking.
To assist in locating the distal tip by fluoroscopy during a procedure, radiopaque markers are applied to the distal tip. Platinum or platinum blends have been applied to the tubing for this purpose. However, previous markers have been subject to wear and other damage while passing through particularly tortuous anatomies.
It would be desirable to combine the use of bump tubing with efficient assembly methods that lower the risk of kinking and provide protection for radiopaque markers.